You currently have javascript disabled. Several functions may not work. Please re-enable javascript to access full functionality.

Register a free account to unlock additional features at BleepingComputer.com

Welcome to BleepingComputer, a free community where people like yourself come together to discuss and learn how to use their computers. Using the site is easy and fun. As a guest, you can browse and view the various discussions in the forums, but can not create a new topic or reply to an existing one unless you are logged in. Other benefits of registering an account are subscribing to topics and forums, creating a blog, and having no ads shown anywhere on the site.

Frustrating Intermittent Issue

Hello Networking geniuses. I'm having a very frustrating issue and I hope someone can point me in the right direction. Also, If these is posted in the wrong section, I apologize profusely, and please feel free to move it to the right section. I don't want to step on any toes.

So this past week I built out 6 Windows 8.1 pro workstations and installed them in a local business. I'm using a Watchgaurd XTM 26 appliance as the router, and there are only about 12-15 total devices on the network. All of the computers are identical in every way, and, if necessary, I can post a PCpartpicker list of the components I used. All I did was build it out, install the drivers on the disk (drivers only, no software), and install an Anti-virus and Microsoft office.

Every computer went in perfectly, and are connected to the internet with no problems..... except one.

The network is laid out fairly simply: The ISP Gateway into the router, then out to a 24-port switch, then from there to each device on the network (including one AP which is used for staff to connect their phones)

The Problem:

This one computer will connect to the network no problem (hard wired connection btw), pull an IP from the router, and have internet access upon boot, but that will only last for 5-10 minutes and then I will lose internet connectivity. Internet connectivity can only be restored by a restart. Sometimes I'll get connectivity randomly back, again for 5-10 minutes before it drops again. Also, all of the other computers say the connection's name, let's call it "Business," but this particular computer says "Network."

What I've tried so far:

The absolute first thing I did since the build was so new and we were using SSD's is I just formatted the hard drive, and reinstalled everything again. When the problem continued, I went online and got the latest driver from Realtek for the integrated NIC, but no change. I then inspected the cabling, and replaced two parts of it (there are 4 cables between the switch and computer. Switch to patch panel, panel to keystone in the office, and patch cable from jack to computer), but even when I'm unable to get internet access, I can still access the NAS and some other mapped drives. Whether the connection is working or not, I still pull the following when doing ipconfig:

IP: 10.0.1.46

Subnet: 255.255.255.0

Gateway: 10.0.1.1

DNS: 10.0.1.1

So I had a USB 2.0 to 10/100 ethernet adapter lying around, so I put that in and installed the drivers and tried that connection, but the problem remains. (I've been doing ipconfig /release and /renew this whole time just fyi)

When the internet is down, I can't ping any websites in cmd OR the router, although I can reach other devices on the network. I've even disabled Windows and the Antivirus firewall, but, like I said, all of the other computers on the network are EXACTLY the same in every way and are all working perfectly.

The only two things I can think to do:

Try using a wireless adapter to see if there is any difference

Re configuring the router/firewall (I don't really think this would do it either because when I lose connectivity it won't even ping the router?)

Also, I get no connectivity if I try and input a static IP address on the router.

If anyone has any suggestions of some things to try it would be great. I'm sorry I didn't include any logs with this post, but it's Sunday and i don't have access to the computer until tomorrow morning. I just wanted to see if I could show up tomorrow armed with a few more things to try to resolve the issue. I appreciate you taking the time to read this long post.

BC AdBot (Login to Remove)

Since you can connect/ping the rest of the network/devices, I'd say the router is the one with the issue for that particular IP address it's not forwarding it on. But the fact you can't even ping the default gateway is a bit weird.

I don't understand this: "Also, I get no connectivity if I try and input a static IP address on the router." Did you mean a static IP on the PC?

I'm actually not sure. I was going to at least move the cable to a different port today, but I didn't have access to the "network" room today (because it's Sunday) when I was troubleshooting. I know it's not a PoE enabled switch, but since it was there when they hired me to come in and set all this up I didn't pay much attention to it afterwards since everything seemed to work when I left it after the install.

If the router is to blame, why on earth would that one computer have issues when none of the others have any? Even if the boards were manufactured at different times, locations, etc., that wouldn't make a difference in how the router see's the computer, right?

I'm just at the point where I've thought so long and hard about the issue that something simple and obvious might occur to someone else.

No no no....if that PC can see the rest of the network - can ping other PCs, connect to printers etc, then it is working just fine. It's not the PC the router is having an issue with it's the IP address the PC has that's its issue. The LAN really never goes above Layer 2 in most cases (yes I know VLANS...shhh) so it's all about the switches. The not being about to ping the router is what's really weird. Also the fact it works for a bit before stopping. If it just couldn't surf then I'd say its a firewall issue somewhere, which I'm not so sure it isn't a firewall issue, it's the not pinging the router that has me baffled.

When it's not working and you do an ipconfig /release /renew dosido do you pull a good IP address?

I'd try safe mode with networking and see if you make it past the 5 - 10 min threshold.

I can't recall off the top of my head what the result of the renew was when I couldn't get internet access. I know what you mean when you say you are baffled, as I'm just as baffled if not more so. So let's just say that when I do boot it in safe mode / networking and it actually works, what would be causing the issue? Some background program? I think this is what I'm going to try:

Install and test wireless card

Make sure switch isn't manageable and swap ports

Temporarily disable hardware firewall

Try workstation in safe mode.

The only thing that sucks is that every time I try something different I have to sit there and continuously try loading pages/pinging until the internet goes down. I've checked the firewall log immediately afterwards and seen activity from that workstation, but nothing that indicates an error or something malicious that would make the firewall deny the computer further access to the WAN. IDK, my brain is kind of mush at this point. Let me know if you can think of anything else to try and I'll report back tomorrow morning on the results.

I popped on over the the Watchgaurd forums, but all the the info on there seems to be really advanced networking stuff, and this is just a very small business office that doesn't even need VPN much less VLANs, proxies, etc. I'm wondering if I've gone overboard and should have bought a simpler firewall.

I think until you are back in front of the PC, it's just a guessing game. I'd let it go till you are there. Unless someone pops on with a different idea, you have some good directions to go when there. Maybe it's something silly =)

Actually had another thought. Since the firewall and router are the same device, I'm wondering in the packets have to clear the firewall to make it to the router portion of the device. This would cause the ping to fail.

Basically, the firewall, although handing out DHCP info for the network, didn't do anything with DNS. That means that the IP config was showing the ISP's DNS info, not the 10.0.1.1. The firewall was stopping the packets from pushing through to the WAN in order to resolve the DNS. I have NO IDEA why this was happening only on this PC and not on any of the others, nor do I know why it was actually working some of the time. All I had to do was forward port 53 (for DNS) and BOOM SHAKA LAKA no more problems. Thank you so so much @CaveDweller2 for taking the time to try and help me out, and also to anyone out there for reading my long posts.